1. Field of the Invention
The present invention relates to a wide-angle zoom lens system suitable for a camera using a solid-state image pickup device, and more particularly to, an inexpensive compact wide-angle zoom lens system having a wide field of view and high magnification.
2. Description of Related Art
Recently, image pickup apparatuses using an image pickup device such as a charge coupled device (CCD) and a complementary metal oxide semiconductor (CMOS), for example, digital cameras and digital camcorders, have been widely used. High performance such as high magnification and a wide viewing angle has been required for the image pickup apparatuses. In addition, there is a demand for inexpensive compact image pickup apparatuses. Accordingly, there is also a demand for inexpensive high-performance compact zoom lenses.
A zoom optic system disclosed in Japanese Patent Application Publication No. 2007-108531 includes first to third lens groups having negative, positive, and positive refractive power respectively, in that order from an object. In the zoom optic system, although a wide viewing angle of 80° or more can be obtained, a magnification has a low value of less than 3. In addition, since the first lens group is constructed with three lenses, it is unsatisfactory for compactness.
A zoom optic system disclosed in Japanese Patent Application Publication No. 2007-102182 includes first to third lens groups having negative, positive, and positive refractive power, respectively. At the telephoto position, the first and second lens groups are moved so as to shorten the distance between the first and second lens groups and lengthen the distance between the second and third lens groups. The zoom optic system has a high magnification of 3 to 4 but a narrow viewing angle of 70° or less.
A zoom optic system disclosed in Japanese Patent Application Publication No. 2005-196621 includes first to fifth lens groups having positive, negative, positive, positive, and positive refractive power, respectively. During image-field shifting from wide-angle to telephoto, the first to fourth lens groups are moved, and the fifth lens is fixed. A partial lens group of the third lens group is designed as a shift lens group. By shifting the partial lens group in a direction substantially perpendicular to an optical axis direction, the image field can be shifted. In this zoom optic system, a high magnification of 7 and a wide viewing angle of 75° or more can be obtained. However, the construction of lenses is complicated and since the zoom optic system has five lens groups, there is a disadvantage in that the lens barrel needs to be large.
A zoom optic system disclosed in Korean Patent Application Publication No. 2001-042218 includes first to third lens groups having negative, positive, and positive refractive power, respectively. During image-field shifting from wide-angle to telephoto, the first and second lens groups are moved and the third lens group is fixed, so that the distance between the first and second lens groups is shortened and the distance between the second and third lens groups is lengthened. However, since the zoom optic system is constructed with six lens groups, there is a disadvantage in terms of an increase in cost.